Generally, a sensory signal output apparatus is an apparatus, such as a speaker, a receiver, a buzzer or a vibratory device (including a vibrator and a linear motor), which converts an electrical signal input from a signal source into a mechanical signal to output sound or vibration.
The sensory signal output apparatus is configured so that a coil is disposed in a gap defined between a yoke and a magnet/top plate sequentially stacked on and fixed to the top of the yoke by bonding or welding in a state in which the coil is fixed to one side of a vibratory plate, and a magnetic circuit package constituted by the yoke, the magnet/top plate and/or the coil and the vibratory plate vibrate in reaction to magnetic flux generated in the gap in a direction of an alternating current signal applied to the coil to generate sound and/or vibration.
The main vibrating member (for example, the magnetic circuit package) collides with peripheral elements during vibration with the result that impact noise is generated or the main vibrating member and the peripheral elements are damaged. In recent years, a magnetic fluid has been used as a shock-absorbing member in order to solve the above problems.
The magnetic fluid is formed at a side of the yoke included in the main vibrating member opposite to the side to which the magnet is mounted along the diameter of the magnet, i.e., at a portion corresponding to the outer edge of the magnet, in an annular shape.
This is because the magnetic fluid is collected to the edge portion of the magnet, on which magnetic force concentrates, according to the properties related to the intensity of magnetic force of the magnet in that the magnet has great magnetic force at the edge portion thereof and the intensity of a magnetic field is increased toward the edge portion of the magnet.